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Plumbing in the Home/The exciting world under the bathroom


Hello Dana,

How are you doing? The bathroom we have in the 2nd floor has a walk-in shower with tiles on the floor and walls. The drain is that kind of metal plate with many round holes and 2 screws, and the drain pipe is 2-3 inch diameter more or less. This is South FL construction from 2007, and the 2nd floor is wood, not concrete.

We're very careful not to let stuff, hair etc go thru the drain. So days ago it started pooling water and taking a while to drain it. I wasn't alarmed b/c I'm confident there couldn't be anything serious in there. So I pulled out some hait from the drain, and everything went back to normal. I was surprised how can a little bit of short hair clog a 2-3 inch wide pipe? While I was "digging" down the drain I felt that after the run of drain pipe that goes vertically down, there's like a wider "chamber" down there and there seemed to be some standing pool of water down there. What is that? Is there a "pan" under the bathroom? Is it normal for water to be sitting down there for 20 about hours or so? How can I check/get rid of any hair etc that could be sitting down there, kind of cleaning that "pan"? There's no access to it, so obviously I'll have to open a "door" thru the wall, maybe make it an access door instead of patching the drywall back again. How can I get the house plans with the details of this type of plumbing installation that's under the floor, inside walls etc? Is that something the county would have or only the builder?

Sorry I have so many questions. Your help is greatly appreciated



Standard shower pan cross-section
Standard shower pan cr  

P trap
P trap  
Hi Rick,
You are right, plumbing systems can be a bit of a mystery for a neophyte.
There is a bit of a joke in the plumbing trades that says; "All you need to know to be a plumber is that water flows downhill, payday is on Friday and don't bite your fingernails." LOL  There actually is a bit more to it than that.

The configuration of most plumbing piping systems is pretty much controlled by Code requirements and the physical structure into which they are installed. I will include a couple of pictures to illustrate what's going on with your shower pan.

The "standing water" you have discovered is actually supposed to be there. It is not a "pan" as you described, it is what is called a "trap" or "p-trap" that provides a water seal in any drain line connected to a sewer system. This water seal prevents sewer gases from coming back up the pipes and entering the living spaces. Not only does it smell bad, it is potentially toxic because it's methane gas.

It is a good maintenance practice to have all of the drain lines in the house cleaned every few years to eliminate any build up of soap scum and other debris that can interfere with water flow.

As for getting the plans to the house, that might be possible but they really won't show the actual plumbing. Pipe routing and other installation details are pretty much left up to the installer (plumber) that is doing the work at the time. The city inspector merely confirms that the work that they are doing complies with current building codes.

There are actually two sets of plans; There are the original set of plans that were submitted for approval to the billing department and, sometimes but not always, a set called "as built" that show any deviations from the original set. As built plans are pretty rare for residential or tract type construction. Those structures go up so quickly and they're pretty much cookie-cutter. That particular plan has been built so many times that the builder has worked out the kinks. Add to this any customizations that the future purchaser may ask for in the original plans may be significantly different from what was actually built.


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Dana Bostick


Pretty much any residential plumbing questions. For "item specific" details such as a specific model of fixture, I will need to research and there may not be any useful information available. Note: I live and work in Southern California. We do not, as a rule, use hot water or steam heating systems, oil fired boilers or private water wells so my knowledge in those areas is pretty limited. There are others here on AllExerts that can probably answer those questions better.


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